The present invention relates to filters for treating a gaseous flow, and more particularly air filters for internal combustion engines.
Air filters known in the motor industry, in particular, usually comprises a case defining a filtering chamber with openings, one of which is the inlet whereas the other is the outlet, these openings communicating with each other through a filter cartridge of a flexible material, this filter further comprising means for supporting said cartridge so that the latter preserves the integrity of its shape. In most cases, the means for supporting the filter cartridge, which may be of an open-cell polyurethane foam, are formed by an independent grate of metal or plastics material which supports the cartridge so as to avoid deformation thereof in the course of operation of the filter. It is known that rather severe stresses are applied to these cartridges if they are employed in air filters for internal combustion engines owing, in particular, to the rather violent fluctuations in the flow of air fed to such an engine. Means for supporting the cartridge are consequently essential.
Now, apart from the fact of being capable of being lost, the presently employed grates of plastics material have the drawback of not lending themselves well to moulding, since there are required in the mould as many retractable cores as there are apertures in the grates, it being understood that the latter has a generally cylindrical shape.